Which war? WWI: We were isolationists until illegal German U-boats sank a United States commercial ship called the Lusitania.
WWII: We were isolationists until December 7, 1941 when the Japanese air fleet surprise attacked and bombed us at Pearl Harbor.
The first, the multiregional hypothesis suggests that humans evolved from Homo erectus outside of Africa. ... The second hypothesis, or the African replacement hypothesis, suggests that Homo sapiens left Africa and then inhabited the rest of the Old World, replacing primitive humans that had already left Africa.
The main reason would be because so many of them had already died fighting against the British.
